1. Field of the Invention
The present invention relates to an insulated type switching device in which at least one of a circuit breaker, a disconnecting switch, a load break switch and a grounding switch is collectively used.
2. Description of the Prior Art
In an electric power receiving and transforming substation, generally an electric power from, for example, an electric power generating company is received via a disconnecting switch and a circuit breaker and the received electric power is supplied to a load, for example, a motor, after the voltage of the received electric power is transformed to a proper voltage for the load. In order to perform maintenance and inspection of the machines and apparatus in such electric power receiving and transforming substation, after interrupting the circuit breaker, the disconnecting switch is opened which is provided separately from the circuit breaker and then the grounding switch is grounded, thereby possible residual electric charges at the power source side and induction current are flowed to the ground as well as voltage reapplication from the power source is prevented, and thus the safety of maintenance and inspection workers is kept. Further, when the grounding switch is grounded while the bus is kept charged, an accident is caused, therefore for preventing such accident an interlock arrangement is provided between the disconnecting switch and the grounding switch.
For example, in a gas insulated switching device as disclosed in JP-A-3-273804(1991), a circuit breaker, two disconnecting switches and a ground switch which are separately manufactured are received in a switch box including insulating gas filled unit chamber and bus chamber, wherein a vacuum circuit breaker is used for the circuit breaker and the movable contact of the vacuum circuit breaker is moved in vertical direction with respect to the stationary contact thereof by means of an actuating mechanism to perform the making and interrupting functions. On the other hand, in the vacuum circuit breaker disclosed in JP-A-55-143727(1980) the movable contact is designed to rotate in left and right directions around the pivotal main shaft thereof so as to perform the making and interrupting functions through opening and closing operations with respect to the stationary contact. In order to perform maintenance and inspection of the machines and apparatus in such electric power receiving and transforming substation, after interrupting the circuit breaker, the disconnecting switch is opened which is provided separately from the circuit breaker and then the grounding switch is grounded, thereby possible residual electric charges at the power source side and induction current are flowed to the ground as well as voltage reapplication from the power source is prevented, and thus the safety of maintenance and inspection workers is kept. After completing the maintenance and inspection work, the grounding switch is at first opened, thereafter the circuit breaker has to be closed. However, in the conventional switching device such series of operations can not be uninterruptedly performed, the respective operations are not easily performed and further the respective switches can not be easily handled.
Further, since the circuit breaker, the two disconnecting switches and the grounding switch are respectively arranged separately, such arrangement makes the entire size thereof large, makes the operation thereof difficult and may cause a possible erroneous operation. Further, when the grounding switch is grounded while the bus is kept charged, an accident is caused, therefore for preventing such accident an interlock arrangement which is complex and strong is provided between the disconnecting switch and the grounding switch, such interlock arrangement limits the arrangement of machines and apparatus therein which further increases the size of the entire device.